Whenever I get into a statistical debate over which player might be better than another the inevitable argument that comes up is “yeah, but player A plays against tougher competition and gets tougher assignments” which is a valid argument to make. But how valid? The other day I looked at a simple, straight forward method for accounting for zone start differences (which can be significant) and today I thought I’d take a look at quality of teammates and quality of competition.
Whenever I browse through my stats.hockeyanalysis.com site or in my own database I have always been curious about the general lack of variation in the quality of competition and to a lesser extent quality of teammate stats (especially over multiple seasons of data) and I thought it would be worth while taking a look at it more closely.
My stats site has a number of metrics that we can look at but let me define a few.
- GF20 – Goals For per 20 minutes of ice time.
- GA20 – Goals Against per 20 minutes of ice time.
- TMGF20 – Weighted average (by ice time played with) of teammates GF20
- TMGA20 – Weighted average (by ice time played with) of teammates GA20
- OppGF20 – Weighted average (by ice time played against) of opponents GF20
- OppGA20 – Weighted average (by ice time played against) of opponents GA20
I also have the same stats for fenwick as well identified with an F instead of a G in the above abbreviations.
So, let’s take a look at a players offensive capabilities. Things that would affect a players GF20 are the players own offensive talents, the offensive talents of his teammates and the defensive talents of his opponents. We know that not all players have the same talent level, but what about the talent levels of his teammates and his opposition? What is the variation among them?
The above table shows the mean goal production (GF20) in blue along with lines representing + and – one standard deviation. Also included is TMGF20 in green and OPPGA20 in red and their + and – standard deviation lines. I have included data for one, two, three and 4 seasons of data and skaters with a minimum of 400 minutes of 5v5 ice time average per season.
As you can see, there is very very little variation in quality of opposition, almost to the point we can almost ignore it. The variation in quality of teammate is significant and cannot be ignored and while it seems to get reduced over time, it’s impact cannot be ignored even when using 4 years of data.
Here is the same chart except using fenwick stats instead of goal stats.
We see pretty much the same thing when we look at fenwick data as we do goal data. There is very little variation in quality of opposition, but significant variation in quality of teammate. What about on the defensive side of things?
All of this tells us that when comparing/evaluating players, the quality of competition a player faces varies very little from player to player and we should be really careful when we use arguments such as “Player A faces tougher quality of competition” because in the grand scheme of things, the quality of competition probably only has a very minor influence on Player A’s on-ice stats. And if you think about it, this probably makes sense. If you have a great offensive player, the theory is your opponents will want to match up their great defensive players against him. But, at the same time you are trying to match up your great offensive player against their weakest defensive players. When at home, you get the line matching advantage, while on the road your opponent does. When all is said and done everything more or less evens out.